Most CB antennas mounted on Class 8 trucks (semis) in North America are rod antennas typically greater than 1 m in length mounted either on the side-view mirrors or on the sides of the cabin.
Hirschmann Car Communication has developed a thin film CB antenna by printing silver material on PET film that can be mounted inside the vehicle between the headliner and the SMC (fiberglass) roof structure of these trucks.
The legal power limit for CB transmitters is 4 watts. However, drivers sometimes install power amplifiers ranging from 60 watts to over 1000 watts in an attempt to improve their range.
The vehicle manufacturer is concerned that one of these high power amplifiers might be used with the thin film antenna and excessive heat buildup might result in smoke or fire in the cabin.